Suddenly inaccurate voltage readings from pixhawk board

I am using a basic analog voltage/current sensor module from Amazon, and I calibrated the voltage multiplier with my multimeter. Everything was fine and it was reading something like 16.5v, but then after a quick flight and landing it now reads 7.5v. I checked with my multimeter and it still said 16v. Should I recalibrate the sensor or is the power module probably damaged?

I’ve had a power brick / distribution board go bad like that too. I would say it is damaged.
Although you also need to measure the voltage measurement signal to the flight controller, it has a maximum of 3.3volts, and should probably read between 1.4v and 1.6v depending on your power brick and exact resistor values. If this value is in that range, then it could be the flight controller that is damaged.

You can easily build your own voltage divider to fix the specific problem this time, but what else will go wrong?
I’d probably purchase something a little more reliable.
What flight controller do you have?